1. Field of the Invention
This invention relates to an image forming apparatus such as an MFP (multi-function peripheral), which is a digital composite machine, or a printer and also to an image forming apparatus and a print control method thereof that improve the printing efficiency of color printing and monochromatic printing.
2. Description of the Related Art
Known image forming apparatus such as MFPs are adapted to process image data that are prepared by a computer or the like for printing images. When monochromatic printing jobs and color printing jobs are input in an arbitrarily determined order, MFPs operate to print images of the printing jobs in the order in which the jobs are received. As a rule of thumb, the number of resources necessary for color printing using four colors of C (cyan), M (magenta), Y (yellow) and K (black) is four times as many as the number of resource necessary for monochromatic printing. Additionally, a long printing time is required for color printing because the printing engine has to be driven four times as long as the time necessary for monochromatic printing.
For the purpose of the present invention, a resource refers to the size of a memory or the capability of a CPU necessary for a printing process. Thus, color printing that processes four colors of C, M, Y and K requires resources four times as many as the resource necessary for monochromatic printing.
When printing a small number of copies by color printing or monochromatic printing after a color printing job or a monochromatic printing job of printing a large number of copies (e.g., more than 100 copies), the printing job of printing a small number of copies has to wait a long time for the completion of the printing job of printing a large number of copies. Such a long waiting time inevitably lower the efficiency of printing jobs.
Jpn. Pat. Appln. Laid-Open Publication Nos. 2001-274999 and 2000-267376 describe an image forming apparatus that rearranges the images to be printed so as to print color images or monochromatic images first and monochromatic images or color images, whichever appropriate, second in order to realize high speed printing when color printing jobs and monochromatic printing jobs coexist.
However, with the techniques described in the above cited patent documents, color images and monochromatic images are rearranged regardless of the number of copies to be printed so that if the first printing job involves a large number of copies and the second printing job is to produce a small number of copies, the second printing job has to wait for the completion of the first printing job.